1. Field of the Invention
The present invention relates to sliding type electronic parts, provided in a vehicle having a gasoline engine installed therein, for use as a sensor for controlling the ratio at which gasoline is mixed with air or as a stroke sensor for controlling the amount of exhaust gas to be recycled.
2. Description of the Related Art
The applicant of the present invention proposes a sensor, including a variable resistor, for controlling the ratio at which gasoline is mixed with air or controlling the amount of exhaust gas to be recycled, as disclosed in, for example, Japanese Utility Model Laid-Open No. 3-104701.
FIG. 12 is a sectional view illustrating a conventional sensor of the above type. This sensor comprises a casing 1 which forms an outer shell; a shaft 2 movable from side to side in FIG. 12 with respect to the casing 1; a pair of projections 3 provided on the shaft 2; a resistance substrate 4 provided within the casing 1; a brush 5 which slidably contacts a conductive pattern (not shown), such as a resistor or current collector, provided on the resistance substrate 4; a slider receiver 6 for holding the brush 5; a return spring 7 for supplying a spring force to the slider receiver 6; and an external terminal 8 connected to the resistance substrate 4. A pair of guide grooves (not shown), extending parallel to the shaft line of the shaft 2, with which grooves the corresponding projections 3 are engaged, are provided in the casing 1. In this sensor, the slider receiver 6 is slid parallel to the shaft line of the shaft 2 in opposition to the return spring 7 due to the pressing force of the shaft 2. The projections 3 and the guide grooves constitute a guide portion for guiding the slider receiver 6 in a direction parallel to the shaft line of the shaft 2.
However, the above-described conventional sensor has a problem as described below. Since a gap of a predetermined dimension is formed between the projections 3 and the guide grooves, the slider receiver 6 vibrates relative to the guide groove due to the vibration of the vehicle, causing the brush 5 to slide very slightly on the resistance substrate 4. As a result, the current-conductive pattern, the brush 5, the projections 3 and the guide grooves wear quite significantly.